This proposal describes our systematic study of the novel reactions of unsaturated diazoketones. In particular, we plan to explore the vinylogous Wolff rearrangement and the acid catalyzed cyclization of unsaturated diazoketones, two reactions which we have recently uncovered and which we are certain will be of considerable importance for the synthesis of compounds of biological and physiological importance. For example, the former reaction is a synthetic alternative of the Claisen rearrangement of enol vinyl ethers, while the latter process provides a new and efficient method for the initiation of mono- and polyolefinic cationic cyclization. In addition to an in depth study of the mechanistic details of these novel transformations we plan to illustrate the general utility of the diazoketone functionality via the development of new synthetic methods and by total synthesis. Here potential routes to the alkaloid tecomanine and several steroidal analogues including estrone and dihydroprogesterone are described. Finally, we will examine in detail the photochemical decomposition of beta, gamma-unsaturated diazoketones. Completion of this research will greatly increase our general knowledge of the unsaturated diazoketone functionality, as well as lead to new synthetic methodology of importance to biomedical research in general.